Method of removing foreign substances from CRDM and device for executing same

Abstract

A method of removing floating foreign substances that may interfere with a normal operation of an electromechanical mechanism of a control rod drive mechanism and a device for executing the same are provided. The method of removing the foreign substances from the control rod drive mechanism comprising a driving shaft including a plurality of teeth and disposed in a vertical direction in the control rod drive mechanism, a first part configured to hold or release a lower end portion of the driving shaft depending on whether a stationary gripper coil is activated, a second part configured to hold or release an intermediate portion of the driving shaft depending on whether a movable gripper coil is activated, and a third part configured to move the second part in the vertical direction depending on whether a lift coil is activated may include: activating at least one of the stationary gripper coil, the movable gripper coil, and the lift coil to drive the first part, the second part, or the third part in a state in which the driving shaft is not able to move; and removing the foreign substances from the first part, the second part, or the third part.

What is claimed is: 
     
       1. A method of removing foreign substances from a control rod drive mechanism comprising a driving shaft including a plurality of teeth and disposed in a vertical direction in the control rod drive mechanism, a first part configured to hold or release a lower end portion of the driving shaft depending on whether a stationary gripper coil is activated, a second part configured to hold or release an intermediate portion of the driving shaft depending on whether a movable gripper coil is activated, and a third part configured to move the second part in the vertical direction depending on whether a lift coil is activated, the method comprising:
 activating at least one of the stationary gripper coil, the movable gripper coil, and the lift coil to drive the first part, the second part, or the third part in a state in which the driving shaft is not able to move; and 
 removing the foreign substances from the first part, the second part, or the third part by driving any of the first part, the second part, or the third part, 
 wherein the removing of the foreign substances from the first part is performed by activating the lift coil to move the second part upward in the vertical direction while the stationary gripper coil is activated to hold the lower end portion of the driving shaft with the first part. 
 
     
     
       2. The method of  claim 1  further comprising:
 inactivating the lift coil to move the second part downward in the vertical direction. 
 
     
     
       3. The method of  claim 2 , further comprising:
 repeating the activating and the inactivating the lift coil. 
 
     
     
       4. The method of  claim 1 , wherein the first part comprises:
 a first latch configured to be latched on any of a plurality of teeth of the driving shaft; 
 a first link having one end connected to the first latch and the other end connected to a first latch plunger; 
 a first latch pole with or without magnetism according to whether the stationary gripper coil is activated; and 
 the first latch plunger pulled or not pulled to the first latch pole according to whether the stationary gripper coil is activated. 
 
     
     
       5. The method of  claim 4 , wherein the second part comprises:
 a second latch configured to be latched on any of a plurality of teeth of the driving shaft; 
 a second link having one end connected to the second latch and the other end connected to a second latch plunger; 
 a second latch pole with or without magnetism according to whether the movable gripper coil is activated; and 
 the second latch plunger pulled or not pulled to the second latch pole according to whether the movable gripper coil is activated. 
 
     
     
       6. The method of  claim 5 , wherein the third part comprises:
 a third pole with or without magnetism according to whether the lift coil is activated, 
 wherein the second latch pole is pulled or not pulled to the third pole according to whether the lift coil is activated. 
 
     
     
       7. The method of  claim 1 , further comprising setting an operation prohibition condition with respect to the lift coil, the operation prohibition condition being a state in which the stationary gripper coil and the movable gripper coil are activated.